Here are the release notes for the most recent version of Islandora, as well as links to the appropriate Github repositories. Islandora is released twice a year. Rather than waiting for the release, some institutions prefer to run closer to the most recent code, where bugs might be fixed or new features added. If you encounter a bug in the release (there are always known issues), it's a good idea to review the Github repository for that module to see if a fix has been submitted. Islandora runs a continuous integration testing framework, which means that new code for Islandora is always tested before being merged.